cox.zph               package:survival               R Documentation

_T_e_s_t _t_h_e _P_r_o_p_o_r_t_i_o_n_a_l _H_a_z_a_r_d_s _A_s_s_u_m_p_t_i_o_n _o_f _a _C_o_x _R_e_g_r_e_s_s_i_o_n

_D_e_s_c_r_i_p_t_i_o_n:

     Test the proportional hazards assumption for a Cox regression
     model fit ('coxph').

_U_s_a_g_e:

     cox.zph(fit, transform="km", global=TRUE)

_A_r_g_u_m_e_n_t_s:

     fit: the result of fitting a Cox regression model, using the
          'coxph' function. 

transform: a character string specifying how the survival times should
          be transformed before the test is performed. Possible values
          are '"km"', '"rank"', '"identity"' or  a function of one
          argument. 

  global: should a global chi-square test be done, in addition to the
          per-variable tests. 

_V_a_l_u_e:

     an object of class '"cox.zph"', with components:

_N_o_t_e:

     The 'plot' method requires the 'splines' library

_R_e_f_e_r_e_n_c_e_s:

     P. Grambsch and T. Therneau (1994), Proportional hazards tests and
     diagnostics based on weighted residuals. _Biometrika,_ *81*,
     515-26.

_S_e_e _A_l_s_o:

     'coxph', 'Surv'.

_E_x_a_m_p_l_e_s:

     data(ovarian)
     fit <- coxph( Surv(futime, fustat) ~ age + rx, ovarian)
     temp<- cox.zph(fit)
     print(temp)                  #display the results
     plot(temp)                   #plot curves

